Lipid:cholesterol acyltransferase enzymes have been known for some time (see for example Buckley—Biochemistry 1983, 22, 5490-5493). In particular, glycerophospholipid:cholesterol acyl transferases (GCATs) have been found, which like the plant and/or mammalian lecithin:cholesterol acyltransferases (LCATs), will catalyse fatty acid transfer between phosphatidylcholine and cholesterol.
Upton and Buckley (TIBS 20, May 1995, p 178-179) and Brumlik and Buckley (J. of Bacteriology April 1996, p 2060-2064) teach a lipase/acyltransferase from Aeromonas hydrophila which has the ability to carry out acyl transfer to alcohol receptors in aqueous media.
A putative substrate binding domain and active site of the A. hydrophila acyltransferase have been identified (see for example Thornton et al 1988 Biochem. et Biophys. Acta. 959, 153-159 and Hilton & Buckley 1991 J. Biol. Chem. 266, 997-1000) for this enzyme.
Buckley et al (J. Bacteriol 1996, 178(7) 2060-4) taught that Ser16, Asp116 and His291 are essential amino acids which must be retained for enzyme activity to be maintained.
Robertson et al (J. Biol. Chem. 1994, 269, 2146-50) taught some specific mutations, namely Y226F, Y230F, Y30F, F13S, S18G, and S18V of the A. hydrophila acyltransferase, none of which is encompassed by the present invention.
WO 2005/066347 relates to variant lipid acyltransferases and methods of making same. These variant enzymes are not encompassed by the present invention.
The development of variant lipid acyltransferases with modified (enhanced) activity has not been without difficulties, particularly in finding variant lipid acyltransferases which have high specific activity in a number of applications.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.